Troubleshooting
Cosmos sulphureus 'Klondike' problems — and how to fix them
Cosmos sulphureus 'Klondike' (Cosmos sulphureus 'Klondike') is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Few flowers, lots of foliage
Caused by rich soil or feeding. Stop fertilising and grow in lean soil to restore prolific blooming.
Leggy, floppy stems
Result of too little light or over-rich soil. Site in full sun and pinch young plants to encourage branching; stake taller stems if needed.
Powdery mildew
White coating on leaves in humid, crowded conditions. Improve spacing and airflow and avoid wetting foliage when watering.
Aphids on new growth
Soft clusters on stem tips and buds. Dislodge with a water jet or use insecticidal soap; cosmos draws beneficial predators that help control them.
Prevent cosmos sulphureus 'klondike' problems before they start
Most cosmos sulphureus 'klondike' issues are care-mismatch, not bad luck. Dial in the basics:
- Common sulphur cosmos problems — the species this cultivar belongs to
- What's wrong with my plant? — the diagnosis apps compared
- Cosmos sulphureus 'Klondike' watering schedule
- Cosmos sulphureus 'Klondike' light requirements
- Best soil mix for cosmos sulphureus 'klondike'
- Cosmos sulphureus 'Klondike' temperature & humidity
- Full cosmos sulphureus 'klondike' care guide
Looking for the species overview? Cosmos — the full care guide.
Cosmos sulphureus 'Klondike' problems — FAQ
Why is my cosmos sulphureus 'klondike' few flowers, lots of foliage?
Caused by rich soil or feeding. Stop fertilising and grow in lean soil to restore prolific blooming.
Why is my cosmos sulphureus 'klondike' leggy, floppy stems?
Result of too little light or over-rich soil. Site in full sun and pinch young plants to encourage branching; stake taller stems if needed.
Why is my cosmos sulphureus 'klondike' powdery mildew?
White coating on leaves in humid, crowded conditions. Improve spacing and airflow and avoid wetting foliage when watering.
Why is my cosmos sulphureus 'klondike' aphids on new growth?
Soft clusters on stem tips and buds. Dislodge with a water jet or use insecticidal soap; cosmos draws beneficial predators that help control them.